Method for treatment of onychomycosis

ABSTRACT

Onychomycosis is treated by grinding the infected portion of a nail down to a level where the nail is not infected and applying a coating of a cyanoacrylate ester to the ground portion which cures to a hard layer. The hard layer can be successively ground and coated with successive layers of cycanoacrylate.

CROSS-REFERENCE TO RELATED APPLICATION

This complete application claims priority from Provisional Application No. 60/593,895, filed Feb. 22, 2005.

TECHNICAL FIELD

The present invention relates to treatment of nail fungi and, more particularly, this invention relates to a novel, effective topical treatment of toenail fungi.

BACKGROUND OF THE INVENTION

Fungi includes yeasts, molds, rusts and mushrooms. Of the 100,000 known species, only 150 regularly cause disease. Dermatophytes which include tinea Mguium are the main cause of onychomycosis the detachment of the nail from its bed at its distal or lateral attachments especially in the dark, sweaty environment of toenails. The fungi create micropores in the nails. They also cause unsightly discoloration and thickening of the nails and attack the tissue in the nailbed under the nails. Continued presence of the fungi can lead to secondary bacterial infections in subjects having poor circulation in the extremities, such as diabetes and eventually to gangrene and amputation of the toes.

20% of the U.S. population between ages 40 and 60 have nail fungus. There are 70 million who have nail and/or skin disease caused by fungi and spend $17.4 billion dollars a year for relief. Topical antifungals used for treatment of toe fungus disease are not nearly as effective against tinea copitis and tinea unguium. The following older topical treatments are still available over the counter (OTC).

The old, but still available

-   -   Whitfield's ointment     -   Tolnaftate     -   Undecylenic acid     -   Topical amphotercian B     -   Haloprogin     -   Castellani's Paint     -   Vick's vaproub     -   Cyclopirox

The following modern OTC topicals are also available. None of these topical treatments provide permanent treatment of nail fungus.

The Modern newer topicals

-   -   Azoles (ketoconazole, econazole, et al.)     -   Polyene antibiotics (nystatin, natamycin)     -   Allyamines (naftifine HCl, terbinafine)     -   Hydroxypyridones (ciclopirox)     -   Morpholines (amorolfine)     -   Selenium compounds (selenium sulfide)

Systematic antifungals such as griseofulvin, Amphotericin B, imidazoles, triazoles, flucytosine or terbinafine must be taken for several months while closely monitoring liver enzymes since there is risk of damage to the liver.

The selling price of typical nail fungus medicines is as follows:

Medication Amount Cost Lamasil (terbinafine) 90 tablets $971.66 Sporanox (traconazole) 84 tablets $797.71 Penlac (cyclopiox 8% laquer) 6.6 ml $147.00

E. M. Warshaw et al. in a double blind study reported (October 2005, American Academy of Dermatology) that continuous ingestion of Lamisil was far superior to pulse therapy and that continuous therapy only provided 71% mycological cure and 41% complete cure. Cure of all nails only occurred in 25% of the subjects.

Nail lacquers may induce side effects such as sensitization and allergic contact dermatitis (European Journal of Dermatology, Volume 10, Number 3, 223-5, Avril-Mai 2000. In a case study, it was found that after preformed acrylic nails bonded with Ethylcyanoacrylate (ECA) were removed after 3 weeks, oncychomycosis was revealed. However, the oncychomycosis reaction disappeared when the nails where photo bonded.

STATEMENT OF THE INVENTION

It has surprisingly been discovered in accordance with the invention that selectively applying a topical coating of cyanolkeinoic esters to fungal areas of diseased nails followed by repetitive debridenment and reapplication of the topical coatings results in an effective elimination of the fungus growth. The fungal growth requires air, a substrate such as keratin and water such as from hot sweaty feet. However, alkenoic esters such as c₁ to c₁₀ cyanoacrylate esters bind to keratin to form a hard film encapsulating the fungus and yeast that grow within keratin. This prevents further growth of the yeast and fungus. The hard film that forms is impervious to water vapor which eliminates another necessary ingredient for fungus and yeast growth. Periodic debrodement of the hard film with encapsulated fungus is necessary to provide complete removal of the fungus from the nails.

Liquids containing Cyanoarcrylate ester such as Cyanoacrylate ethyl have chemical properties capable of effectively controlling fungal nail disease. When such a liquid is applied to the surface of a toenail or fingernail infected with Onychomycosis, these chemicals can penetrate beneath the nail surface and coat or fill the micro pores created by fungi. After the liquid has been applied to the nail (about 3 to 5 minutes), the liquid solidifies. Nails treated with the liquid harden. The nail/hardened plastic is sufficiently durable to maintain its condition for up to six weeks. The hardened plastic effectively forms a moisture barrier. Without moisture, onychomycosis is incapable of further nail degradation and the disease is controlled or even eliminated.

Cyanoacrylate ester such as Cyanoacrylate ethyl have high absorbing ability; they are good vehicles for delivery of other antifungal medications such as Clotrimazole, Nystatin Griseofulvin, Ketoconazole, Terbinafine, Itraconazole and others. Therefore, mixing a cyanoacrylate ester with one of the antifungal medications may have an enhanced treatment effect on Onychomycosis fungi. Addition of 1-12%, preferably 2-10% of undecylenic acid has been shown to inhibit the spread of infection and to remove the yellow-color of infected nails as does the presence of a small amount of hydroquine.

The fungus infected nail becomes microporus. The viscosity of the coating solution is selected such that the solution enters the pores and progresses through the thickness of the nail to the nail bed.

The compound that provides the popular cyanoacrylate, SUPERGLUE with adhesive properties is methyl cyanoacrylate.

The esters of alkenoic acids have the general formula:

Where R is a hydrocarbon group having 1 to 12 carbon atoms, preferable an alkyl group having 2-8 carbon atoms.

The preferred ester is ethylcyanoacrylate (ECA) through many of the other commercially available esters where R is ethyl, propyl, butyl octyl, or their mixtures, are available and will form impervious, films.

Contrary to popular understanding, cyanoacrylate does not air dry. In fact, cyanoacrylates cure (convert from liquid to solid) in the prescense of weak bases such as water, alcohol, and blood. At normal conditions, a thin layer of water is present on almost all surfaces. This accounts for many unintended adhesions involving appendages and/or expensive tools. The curing process involves the anionic chain polymerization reaction, which occurs as follows: In the chain-initiating step, the weak base (X) donates an electron pair to a cyanoacrylate monomer. The CH₂ group is highly electropositive as a result of the electron-withdrawing properties of the cyanide and ester groups; therefore, the electron pair is attracted to this region. The attraction alters the carbon-carbon double bond to create bonding sites of both ends of the reactant group.

In this manner, the electron pair is passed on in chain propagation as each monomer alters the next. Bonds from between monomers, ultimately creating the powerfully adhesive polymer changes of cured cyanocnlate glue.

FORMULA 2-ETHYL CYANO ACRYLATE OR (2-ETHYLCYANO 2-PROPENOATE)

PROPERTIES Liquid State Super Glue Chemical Base Ethyl Cyanoacrylate Viscosity, cps 30-70 Color Colorless Liquid Vapor Pressure (@ 70° C., mmHg) 10 Specific Gravity (25° F./4° C.) 1.06 Flashpoint TCC ° F. (° C.) 185 (85) Soluble In: Acetone, MEK, Nitromethane Cured State Super Glue Softening Point 306° F. (153° C.) Melting Point 365° F. (185° C.) Temperature Range −65° F. to +180° F. (−54° C. to +82° C.) Rockwell Hardness (M) 74 Typical Gap (Inches) .004 Soluble In: Pacer X-8 Debonder, Acetone, Nitromethane Tensile Strength, steel, ASTM-D2095 4700 psi Impact Strength, steel, ASTM-950 7-10 ft-lbs Tensile Shear Strength, ASTM-D1002 (psi) Steel 2500 Aluminum 1600 ABS  665* Nylon  850* Rigid PVC  700* SBR  85* EPDM  100 *substrate failure

Application and Cure Characteristics:

For best results, use a minimal amount of adhesive. In general, one free falling drop covers one square inch of nail area with a thickness of approximately 002″ for best results. Fixture time and full cure rates are dependent upon temperature, relative humidity, thickness, and surfaces being bonded.

Cyanoalkenoic ester adhesives are actually a solution of prepolymers of the ester in the ester monomer. Viscosity is adjusted by the degree of polymerization of the ester. Preferred viscosity of an ECA is 5 cP to 10 cP which will fill micropores from 0.002″ to 0.005″. Cure rate is affected by the amount of an intribitor cush as 100-2000 ppm of hydroquinone or methyl-ethyl hydroquinone (MEHQ). The monomer can also act as a solvent for other antifungals, such as 0.01 to 5% of preferably 0.1 to 5% undecylenic acid. An additional film forms such as below 10% by weight, suitably 1 to 9% of a compatible acrylic polymer which dissolves in the cynoacrylate monomer such as polymethylmethacrylate may also be present.

To obtain the most effective treatment, the nail area infected with Onychomycosis fungi should be removed to the extent reasonably possible preferably by first mechanically grinding away the infected nail down to the level of the normal nail, and then secondly applying a small amount of the composition. Care should be taken to make certain the composition covers the infected area and also that sufficient amounts are used to saturate as well and to produce a thin coating on the infected area of nail. Applications can be with or without a brush, while not accidentally spilling onto the skin. Skin application can cause a bonding with keratin in skin in a matter of seconds and may be difficult to remove.

Grinding and recoating can be repeated from at least 3 days to 6 weeks, preferably, every one to three weeks for a total of three to four months. The coating usually starts to lift at edges after 1 week. Further treatment can be assigned to the patient to do further debridment with an emery board or other tool at home and using a drop or brush application for the composition.

The following composition for the treatment of onychomycosis was prepared:

Weight Percent Ethylcyanoacrylate 90.4 Hydroquanone 0.4 Undecylcnic acid 0.1 Polymethylmethacrylate 9.0

Methods

237 patients between the ages of 10 years and 100 years were enrolled by a podiatrist and a dermatologist.

1. Duration of nail disease: months to decades (onset World War II, Korean War, Vietnam War, etc.)

2. Secondary diseases: diabetes, hypertension, hypercholesterolemia, obesity and osteoporosis.

3. Pretreatment diagnosis: clinical, KOH, PAS-D of nail clippings and cultures on Sabaround's agar.

4. Clinical improvement assessed with: a) patient satisfaction, b) color, c) thickness and d) new unaffected nail growth.

5. Initial visit: cultures, photos, debridement with Dremel® sanding tool and then application of topical test material. This was repeated at 1 or 2 week intervals dependent upon severity of nail disease for the 2^(nd) and 3^(rd) visits.

6. Subsequent visits: At 1 or 2 month intervals dependent upon patient's ability to home treat with emery (sandpaper) boards and home application brush tipped tubes of medication.

Results

1. Clinical Evaluation:

-   -   Patient Satisfaction 85%-95% at 1-2 months     -   Color Improvement 80%-90% at 2-3 months     -   Reduced Thickness 92%-95% at 2-4 months     -   Normal Proximal Nail 80%-85% at 2-3 months

2. Toenail Culture Data:

-   -   Subgroup I-patients followed up to 9 months:     -   17 negative cultures in 107 patients     -   Subgroup II-patients followed up to 5 months:         -   2 negative cultures in 32 patients     -   Subgroup III-patients followed less than 5 months:         -   95 patients culture pending or positive

Discussion and Conclusions

1.16% Negative cultures at 9 months in toenails reflects the slow growth of these nails and the layer by layer removal of infected keratin by successive debridement.

2. Cost in California of 90 tablets of terbinafine January 2006 was $971.66. 84 tablets of itraconazole sold for $797.71. Six ml of ciclopirox lacquer cost $147.00 (a lacquer is analogous to a coating or paint and is not bound to keratin like cyanoacrylate).

3. Cyanoacrylates have been safely used in medicine for years in wounds, ENT, opthalmology and cardiac surgery.

4. Cyanoacrylate glues used in securing artificial nails deteriorate over time and water permeated between the natural and artificial nail allowing fungus to attack the natural nail.

5. An composition comprising cyanoacrylate with hydroquinone and undecylenic acid (in low concentration) combined with periodic debridement provides a less expensive, effective, safe non oral alternative for the treatment of nail fungus.

Conclusion

A less expensive, safe, yet effective non oral therapy for onychomycosis is provided that benefits:

1. Patients unable to tolerate oral medication for health or financial reasons and

2. Those seeking a more effective topical alternative.

3. Onychomycosis can be treated with a composition of cyanoacrylate and hydroquinone, optionally including unrdecylenic acid.

4. Hydroquinone and unrdecylenic acid help bleach yellow imperfect nails.

5. Dermatophytes need A) air B) food=keratin C) water

6. Cyanoacrylate binds to keratin of skin and nails blocking these essential needs.

7. Hydroquinone helps bleach yellow color of infected nails.

Dramatic clinical improvement was evident within weeks after the first appointment for debridement and application of the TCA composition.

Summary

-   -   Clinical-patients pleased early in course     -   Culture-comparable to better than oral antifungals     -   Conclusions-safe, effective, inexpensive     -   Significant, cost savings     -   Benefits-no drug interactions

COST and OUTCOME COMPARISONS New topical strategy Conventional 1. Initial office visit & 1. Initial visit and labs Treatment (Debridement, 2. Rx of $1000 or +/− less Application of ECA 3. Follow up labs (cost of topical) 4. Debridement may be needed 2. Follow up visit with 5. Cure rates of 40-70% Debridement (topical) and only 25% complete 3. Follow up and cure of all nails reapplication of (Warshaw et al. JAAD same again. Then complaint, October 2005) flexible patient can continue home treatments for 6-12 mo or longer if chronic disease 4. Mycological cure 40-70% with complete cure of all nails possible and easily maintained.

It is to be realized that only preferred embodiments of the invention have been described and that numerous substitutions, modifications and alterations are permissible without departing from the spirit and scope of the invention as defined in the following claims. 

1-11. (canceled)
 12. A composition for the treatment of a nail infected with onychomycosis comprising in parts by weight: Cyanoacrylate   70-95 Inhibitor .05-5 Anti fungal agent 0.05-5 


13. A composition according to claim 12 further including 0.1 to 15% of an acrylic film forming polymer soluble in cyanoacrylate monomer.
 14. A composition according to claim 13 in which the acrylic film forming polymer is polymethylmethacrylate.
 15. A composition according to claim 12 in which the antifungal agent is undecylenic acid.
 16. A composition according to claim 12 in which the cyanoacrylate is 2-ethyl cyanoacrylate. 